Demonstration of a third-order hierarchy of topological states in a three-dimensional acoustic metamaterial

Matthew Weiner; Xiang Ni; Mengyao Li; Andrea Alù; Alexander B Khanikaev

doi:10.1126/sciadv.aay4166

Demonstration of a third-order hierarchy of topological states in a three-dimensional acoustic metamaterial

Sci Adv. 2020 Mar 27;6(13):eaay4166. doi: 10.1126/sciadv.aay4166. eCollection 2020 Mar.

Authors

Matthew Weiner^{1

2}, Xiang Ni^{1

2

3}, Mengyao Li^{1

2}, Andrea Alù^{1

2

3}, Alexander B Khanikaev^{1

2}

Affiliations

¹ Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, 140th Street and Convent Avenue, New York, NY 10031, USA.
² Physics Program, Graduate Center of the City University of New York, New York, NY 10016, USA.
³ Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY 10031, USA.

Abstract

Classical wave systems have constituted an excellent platform for emulating complex quantum phenomena, such as demonstrating topological phenomena in photonics and acoustics. Recently, a new class of topological states localized in more than one dimension of a D-dimensional system, referred to as higher-order topological (HOT) states, has been reported, offering an even more versatile platform to confine and control classical radiation and mechanical motion. Here, we design and experimentally study a 3D topological acoustic metamaterial supporting third-order (0D) topological corner states along with second-order (1D) edge states and first-order (2D) surface states within the same topological bandgap, thus establishing a full hierarchy of nontrivial bulk polarization-induced states in three dimensions. The assembled 3D topological metamaterial represents the acoustic analog of a pyrochlore lattice made of interconnected molecules, and is shown to exhibit topological bulk polarization, leading to the emergence of boundary states.

Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).